Our team, the ProfeSSoRs, created BathMate — an attachable bathroom extension that aids individuals with Chronic Fatigue Syndrome to bathe themselves independently without the need for a personal caretaker or external aid. The device uses two stepper-motor-driven lead screw mechanisms to move a silicone brush across a user's back and includes an integrated peristaltic soap pump, all controlled through four buttons mounted on the board. BathMate allows the user to remain fully seated throughout the entire bathing process, with no overhead reaching or significant arm movement required.
Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a severely debilitating condition affecting millions of individuals across the United States, stripping them of their ability to perform even the most basic daily tasks. Approximately 3.3 million U.S. adults are currently living with ME/CFS, not accounting for the countless individuals that go undiagnosed. ME/CFS is more than persistent tiredness; it is a complex multisystem disease characterized by severe fatigue, cognitive dysfunction, and post-exertional malaise that does not improve with rest. The functional consequences are profound, with approximately 1 in 4 people with ME/CFS so severely disabled that they cannot leave their home or even get out of bed, leaving them unable to perform fundamental hygienic behaviors such as bathing.
For this population, the limitations are not a matter of motivation but a genuine physical impossibility. Existing solutions such as Humanwash, SWITLE Body, and Sit & Shower are either discontinued, prohibitively expensive (ranging from $1,634 to over $5,000), designed for caregiver-assisted use rather than independent operation, or still require significant standing and arm movement. BathMate was designed to solve all of these problems at once, with a total build cost of $153.12.
BathMate is designed to meet the needs of people with CFS or other fatigue-related disabilities who struggle to perform basic hygiene tasks independently. We are specifically targeting people with moderate to severe symptoms who cannot complete bathing in a single session due to limited energy reserves and the risk of post-exertional malaise. For these individuals, even simple movements such as standing, lifting the arms, or maintaining balance can be physically exhausting and lead to prolonged symptom flare-ups.
Our device is designed for users who value independence but lack the physical capacity to bathe without assistance. It may also benefit individuals with similar conditions such as fibromyalgia, where fatigue and endurance limitations are significant barriers. By reducing the physical effort required for bathing, the device enables users to maintain personal hygiene while preserving energy, supporting both their physical well-being and sense of autonomy.
The team used a structured, iterative design process evaluated against 18 requirements organized into User, Functional, Physical, and Documentation categories. A Pugh chart compared each version against a baseline reference of a user cleaning themselves normally without support. Below are the four main iterations of the design.
Version One: Rack and Pinion
The preliminary design included a rack-and-pinion on the horizontal axis to move the brush, designed with 16-inch and 24-inch racks to accommodate all individuals. However, when assembled, the rack would move off the 24" board during brush movement, and slight misalignment between the two racks caused the brush to move at a slower rate. The design also failed to reduce arm movement and did not meet size or corrosion-resistance requirements.
Version Two: Double Lead Screw
By shifting to a double lead screw mechanism for all axial motion, this version successfully corrected the size limitations and significantly reduced user arm movement. The ABS backboard was fabricated by fusing three 12" x 16" sheets using epoxy and acetone. Soap dispensers and the brush assembly had not yet been added at this stage of development.
Version Three: Brush and Soap Tubing
The next iteration introduced the silicone brush scrubber and soap dispenser tubing connected to a 12V peristaltic pump. Although the design successfully met the hypoallergenic material requirement, it was less effective at reducing arm movement during use. The soap box was detached from the board, the brush remained unstable, and the electrical wires were still exposed — a safety concern in a wet environment.
The final version successfully hid the wiring and attached the soap dispenser onto the board. It includes coded step sizes for the motors determined through Design Study 1, and provides a stable brush using additional 3D-printed CAD components — including a brush holder that attaches the brush to the lead screw and a brush stabilizer that keeps the brush upright during movement. The backboard is ABS, the lead screws are aluminum and metal, and the tubing is attached to a peristaltic pump that pushes soap up to the silicone brush. Three suction-cup hooks allow tool-free wall mounting in any standard shower or bathtub.
Version 4 allows the user to remain fully seated without overhead reaching and meets all physical size, weight, and budget constraints. All five Level 1 critical requirements were successfully met. The one remaining limitation is that the control buttons are located on the backboard itself rather than on a wireless remote — identified as the top priority for future development.
Three design studies guided the key decisions in BathMate's final design.
Optimal Motor Speed
The first design study looked into the speed of all three modes of the device, ranging from slow to normal to fast. Six motor speeds were tested, from 25% (80.75 RPM) to 100% (323 RPM) of maximum output. Each trial was observed for stability and effective cleaning quality. The maximum speed caused the gantry to rock and become mechanically unstable. The two slowest speeds took too long to complete a full cycle and were not practical for end users. The top three performing speeds, Fast (75%, 242.25 RPM), Med-Fast (63%, 203.49 RPM), and Normal (50%, 161.50 RPM), were selected as the three user-accessible speed settings and encoded into the final firmware.
Full-Cycle Timing
The second design study aimed to standardize the speed of the device. One of the major requirements is for BathMate to complete a full wash of the user's back in a reasonable amount of time (under 10 minutes). Three trials per speed mode measured the time for BathMate to complete one full cleaning cycle, moving downward while traversing horizontally, then returning to its starting position. All three speeds completed a full cycle well under the target: Fast averaged 1.95 minutes, Med-Fast averaged 2.32 minutes, and Normal averaged 2.93 minutes. This is critical for ME/CFS patients, who cannot remain in one position for extended periods without triggering symptom flares.
Soap Box Placement
Design Study three tested the placement of the soap dispenser caddy across all four corners of the ABS board. Each position was evaluated across three trials measuring prime time (how long for the soap to fully coat the brush), evenness of soap coverage on a 1–5 scale, drip/leakage on a 1–5 scale, and coverage time. Top-corner placements were eliminated because they would require patients to raise their hands above their heads — a motion that can worsen ME/CFS symptoms by causing blood to flow to the feet. The bottom-right corner was selected for its fastest priming time (5.90 s average), highest evenness score (4.33/5), lowest drip (1.33/5), and close proximity to the electronics box housing the peristaltic pump.
Of the 18 requirements evaluated, BathMate's final design met all five Level 1 critical requirements: the user remains seated and supported throughout bathing, the device is operable by one user without assistance, arm movement and overhead reaching are minimized, the non-slip suction cup mounting prevents shifting during use, and the design weighs under 10 lbs. Additional requirements met include hypoallergenic contact materials, tool-free installation in standard tubs and showers, a cleansing cycle completed within 30 minutes, and a final build cost of $153.12 — under the $175 budget. The one unmet requirement across all versions is a wireless remote control for the buttons, which is the top priority for the next iteration.
Future improvements include using PVC covers and waterproof rubber insulation to better protect wiring and piping while creating a cleaner and safer design. Aluminum or stainless steel panels could also be added to improve durability and corrosion resistance. Future work will also focus on creating a more advanced user interface with clearer buttons and improved spacing, along with adding a remote-control system for easier user interaction and customizability. Currently, the electrical box is quite large and could potentially make contact with the user's back during use, so a more optimized and compact electrical box is also a priority for the next iteration.
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The poster below was presented at the Assistive Technology showcase. You can scroll through it or open it in full screen.